The present invention relates to a drive system for an electrochromic display device and, more particularly, to a drive system for uniforming the coloration condition in an electrochromic display device.
In an electrochromic display device of the segmented type, it is strictly required that each colored segment shows the same coloration degree to enhance the legibility. The coloration degree is determined by the charge density applied to the display segment at the coloration operation.
One method for uniforming the coloration degree of the display segments is proposed in copending application, UNIFORM COLORATION CONTROL IN AN ELECTROCHROMIC DISPLAY OF THE SEGMENTED TYPE, Ser. No. 893,513, filed on Apr. 4, 1978 by Hiroshi Hamada, Hiroshi Take, Yasuhiko Inami and Hisashi Uede, and assigned to the same assignee as the present application, wherein the colored segments are electrically connected with each other immediately after completion of the coloration operation.
The present inventor has discovered that transient current flows between the colored segments if the colored segments are electrically connected with each other immediately after completion of the coloration operation. The transient current will create differences of the coloration degree among the colored segments.
Accordingly, an object of the present invention is to provide a novel drive system for an electrochromic display device of the segmented type.
Another object of the present invention is to provide a drive system for an electrochromic display device of the segmented type, which uniforms the coloration degree of each colored segment.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
To achieve the above objects, pursuant to an embodiment of the present invention, the coloration voltage signal is applied only to display segments which should be changed from the bleached state to the colored state. The remaining display segments inclusive of display segments continuously maintained in the coloration condition do not receive the coloration voltage signal. After completion of application of the coloration voltage signal, each segment is held at an electrically opened memory state for a predetermined period of time, for example, five seconds, and then the display segments placed in the coloration condition are electrically connected with each other to uniform the coloration degree.